The following publications are representative of the most relevant prior art known to the Applicants at the time of filing of the application.
U.S. Pat. Nos.
224,970 Feb. 24, 1880 W. L. Teter
2,442,088 May 25, 1948 C. Kreutzer
2,807,919 Oct. 1, 1957 S. P. Bruce
2,885,276 May 5, 1959 G. Upton, Jr.
3,252,775 May 24, 1966 B. Tocri-Guilbert
4,459,779 July 7, 1984 J. C. S. Chen
Hand tools used by carpenters for wood working in both industrial and do-it-yourself projects must be resharpened from time to time. Either man-made or naturally occuring abrasive stones are used for this tool sharpening purpose. Naturally occuring corundum, sold as "India stone", is an alumina abrasive found in Arkansas and other places that is satisfactory for this use but man-made vitrified or organic bonded stones may be found more satisfactory from the standpoint of the control of the abrasive action for accomplishing the desired resharpening of the woodworking tool. The man-made sharpening stones, for example, can be made with a relatively coarse abrasive grit in the range of 180 U.S. Sieve grit size to as fine as 1000 grit size. The coarser grit sizes are used to remove the metal of the tool to sharpen the carpenter's tool more rapidly while the finer grit sizes are used for completing the sharpening process and the finest grits are adapted to ultimately produce a mirror finish on the tool if that is desired. Thus it is usual to use several different sharpening stones having coarser to finer grits in sequence as the tool dressing process proceeds, the stones being lubricated with either water or oil as is well known. A newer type of man made sharpening stone for hand tools that is an organic bonded product used with water, is known as a "Japan stone".
During use, the exposed grits on the sharpening stones become dulled and the stones ultimately wear down to have a concave shape several thousandths of an inch deep in the area where the bulk of the sharpening action takes place, making the stone less efficient for sharpening the tools. Heretofore, such worn stones have either been discarded or subjected to a time consuming lapping operation to recondition the working face of the sharpening stone to have a planar surface.
It has been proposed in the past to provide resin bonded abrasive bodies for various uses such as is shown in the following U.S. Pat. Nos.:
2,885,276 to Upton, Jr. May 5, 1959
3,252,775 to Tocci-Guilbert May 24, 1966
4,459,779 to Shen July 7, 1984
And, dressing tools for sharpening various types of grinding devices are shown in the following U.S. Pat. Nos.:
224,970 to Teter Feb. 24, 1880
2,442,088 to Kreutzer May 25, 1948
2,807,919 to Bruce Oct. 1, 1957
The present invention provides a foam bonded abrasive means that is an improvement over the abrasive structures shown in the above patents. The prior art disclosures show examples of abrasive wheels and coated abrasive products such as the resilient wheel and flexible coated abrasive of U.S. 2,885,276. The polymerized elastomeric bond described in this disclosure as stated in column 9, line 20, provides a grinding and polishing wheel that "does not load or fill" because of the "constant flexing of the bonding film in three dimensions". Likewise, the coated abrasive type product similarly included the flexible foamed bond feature which permits the abrasive grains to give somewhat in their sockets.
Likewise, U.S. Pat. No. 3,252,775 describes a foam bonded abrasive wheel that has a resilient characteristic making it particularly useful for graining wood and polishing metal and the like. The main thrust of this invention is to provide reinforcement for a rotary polishing means to prevent distortion or indeed disintegration during use.
U.S. Pat. No. 4,459,779 teaches the manufacture of a foam bonded abrasive pad that "will not break apart under high speed rotation during grinding". This product is especially designed for use on magnetic recording disks.
U.S. Pat. No. 224,970 merely illustrates a hand held tool for dressing mill stones. The dressing means A may be made of any "suitable" material.
U.S. Pat. No. 2,442,088 shows a manual tool for dressing rotating grinding wheels.